The proposed four-year K01 Population Research Scientist Development Award supports the development of Dr. Kari White as an independent social scientist and public health researcher conducting studies of the impact of health service delivery models and policies on access to and use of highly effective contraception, with the aim of reducing disparities in unintended pregnancy. This is relevant to the NICHD mission and stated interest in research relevant to ensuring that women and men have access to safe, effective and acceptable contraceptive methods. Dr. White brings her solid training in the demography of fertility and use of qualitative and quantitative research methods to the study of contraceptive use. Her career development plan has three main goals: 1) develop expertise in methods to evaluate health services and policy from the individual perspective; 2) gain in-depth knowledge of contraceptive methods and exposure to how contraceptive services are provided; and 3) acquire advanced statistical skills and proficiency working with new data sources to analyze policies and health outcomes. These goals will be met through formal coursework, mentoring from sponsors, directed study with expert advisors, clinical observation, and conferences. She will integrate her current knowledge and skill set with those gained through the career development activities by conducting a study of the individual-, provider- and health systems-level factors contributing to the underutilization of vasectomy among low-income men in the United States. Greater use of vasectomy has the potential to reduce income-based disparities in unintended pregnancy, but there has been limited study of why this method is so little used among low-income men. To comprehensively examine the factors shaping both the demand (individual-level) and supply (provider- and health systems-level) of vasectomy, the research project aims to: 1) assess knowledge, attitudes and interest in vasectomy among low-income men who do not want more children; 2) identify barriers to providing vasectomy services to low-income men among providers at publicly funded family planning organizations and health centers; and 3) evaluate whether expanded Medicaid family planning coverage for low-income men increases vasectomy use and identify the characteristics of men getting vasectomies through the program. In sum, this career development award will provide Dr. White the structured mentoring, advanced multi-disciplinary training, and experience conducting original research that will facilitate her transition to an independent investigator leading studies on contraception. These studies will allow her to make significant contributions to understanding one of the key determinants of unintended pregnancy and that can be used to inform clinical practice and health policy.